This invention relates generally to inter-vehicle information transfer and, more particularly to an automatic inter-vehicle traffic condition message protocol.
Traffic hazards and overcrowding on highways are aggravated by the fact that drivers about to enter a jammed area of highway cannot take alternate routes to avoid such jams. By the time they are aware of a traffic jam, it is often too late to do anything but wait for the jam to clear. The most ubiquitous solutions in existence use news alerts (typically via the radio). Wireless devices capable of accessing the internet also alert drivers to traffic jams through on-line traffic reporting web sites. In general these are handheld and are becoming generally not appropriate for an in-vehicle use because they demand the driver""s attention.
Traffic jam alerts that come across a radio are the result of a drivers"" calls that report traffic conditions, or the result of helicopter reports. Both of these reporting mechanisms rely on human observations of a snapshot of the traffic situation. Only conditions that happen at the moment are reported. Traffic jams occur (and disappear) spontaneously, and so change the particular conditions, and if the radio is not turned on, the driver might not have any awareness of even the most up-to-date information.
Even if a driver is alerted to a traffic jam enroute soon enough to take measures to avoid the jam, the driver may not be familiar with the area, and may have no knowledge of potential detours around the jam. Furthermore, not all roads are monitored. On-line web sites combined with wireless devices allow the driver to be alerted to traffic incidents, but the problem of getting accurate up-to-date reports of constantly changing conditions remains.
Real-time traffic information can be collected by vehicles on the road. This information can be exchanged among vehicles. Vehicle-to-vehicle data communications mainly consist of the continuous, routine exchange of telemetric data such as vehicle status, speed, and acceleration. An ad hoc network can be formed of these vehicles as they travel on the road in the vicinity of one another and exchange information. Their electronic signals can travel over, for example, independent wireless local area network (LAN) communication systems. Wireless LANs use radio and infrared airwaves to communicate information from one point to another without relying on any physical connection. Independent wireless LANs connect Personal Computers (PCs) through wireless adapters. Any time two or more wireless adapters are within range of each other, they can set up an independent network. These on-demand networks typically require no administration or preconfiguration.
An ad hoc network is one in which mobile units interact with one another without a centralized infrastructure. Another characteristic of an ad hoc network is that mobile units may not continuously remain in range of each other, thus the topology of the network is maximally dynamic. This characteristic alone makes the transmission of extensive amount of administrative information among mobile units infeasible.
Many protocols support ad hoc networking. The main differences among the protocols are the amount of administrative overhead and the presence or absence of transmission loops in which a packet moves infinitely around the network. Examples of ad hoc networking protocols are the Destination-Sequenced Distance-Vector (DSDV) protocol, Dynamic Source Routing (DSR), and Ad Hoc On-Demand Distance Vector (AODV) routing protocol. In DSDV protocol, route tables are stored at each node, and each node periodically transmits updates often enough so that every mobile computer can locate every other mobile computer in the collection. The DSR protocol is designed for multihop wireless ad hoc networks of mobile nodes in which the nodes can move continuously and at any time, but the speed with which they move is moderate relative to the packet transmission latency and wireless transmission range of the network hardware. In the AODV routing protocol routes are discovered on an as-needed basis and are maintained only as long as necessary.
Standards are currently being developed to govern the protocol exchange and message format among vehicles in an ad hoc network. Multiple levels of protocols are required to support sophisticated communications among vehicles. Physical device handshaking occurs at one protocol level, while data packaging handshaking occurs at another. Still another level can involve the xe2x80x9cprotocolxe2x80x9d of the sequence of messages, acknowledgements, and error paths that enable cooperative operation among participants in the ad hoc network.
Three U.S. standards relevant to delivering to the mobile traveler real-time information about the current and predicted roadway conditions, the weather, etc. are being developed. All involve various types of position-location information transported electronically. All are message formatting standards, rather than presentation standards. All provide a message structure definition, but do not specify content or quality of data, or the presentation of the data. J2353 (a data dictionary standard) and J2354 (a message set standard inside of which is link data consisting of congestion and speed data) are targeted to individual traveler needs These standards specify the transactional messages needed to exchange a profile and receive back current or on-going status of relevant roadway events. J2369 (a reduced bandwidth standard) was developed for broadcast use, and also for use over reduced bandwidth media hosts such as are typical of mobile systems. In this context, broadcast implies that the function of discarding non-relevant information (e.g. traffic events outside of the traveler""s concern) is left to the client side device.
U.S. Pat. No. 5,621,798 discloses a wireless cooperative messaging network. In this network each unit that can send or receive messages is used as a transmitter/receiver station for the network. Periodically, messages are transmitted or retransmitted from each mobile unit to the others and possibly to a central receiving/transmitting station. Messages are tagged by time and unique identifier. Each vehicle is assigned a transmission window in this system.
U.S. Pat. No. 5,428,544 discloses a system in which vehicular information is interchanged among vehicles traveling along a highway. This information includes speed and direction of the vehicle, and other information that could be processed by other vehicles to determine the local traffic situation. The exchanged data are processed by an on-board computer that interprets the positions of the other vehicles and applies techniques to assess the traffic situation. Traffic information that is exchanged is xe2x80x9craw dataxe2x80x9d, that is, the on-board computer must apply interpretation of the data to determine traffic conditions. Examples of data exchanged are coordinates of several points passed by the sending vehicle and average driving speed and longest halting time between the points.
U.S. Pat. No. 6,092,020 discloses a system that collects individual reports from xe2x80x9cfloating carsxe2x80x9d, the reports being transmitted to and interpreted by a central location. Traffic jams in this system are identified by characteristic fluctuations in speed. In this system, threshold values of speed are set, and when these thresholds are crossed, a traffic situation is inferred and transmitted to a central receiving station.
What is needed is real-time traffic characterization information that is collected and shared by vehicles traveling in the vicinity of one another. A vehicle collecting such information could automatically suggest rerouting to the vehicle""s operator should a traffic jam be detected. Combined with a mapping and route planning system, dynamic adjustments to a vehicle operator""s route could be made automatically, so the operator would not need any knowledge of the travel area (and thus of any potential detours).
The problems set forth above as well as further and other problems are solved by the present invention. The solutions and advantages of the present invention are achieved by the illustrative embodiment of the invention described hereinbelow.
The system of the present invention comprises (1) a traffic characterization protocol operating on an ad hoc communications network among cooperating mobile units, the protocol serving to sequence the flow of traffic characterization data among cooperating mobile units, and (2) a traffic characterization data detection, reception, and computation system that enables the identification of geographic areas of traffic concern. Utilizing conventional in-vehicle computers and conventional wireless LAN transceivers, a plurality of vehicles so equipped, and further containing the system of the present invention, can form an ad hoc distributed real-time traffic condition alert mechanism. As a traffic jam occurs, the vehicles send out traffic characterization data in a sequence defined by the message content and traffic characterization protocol of the present invention. Nearby vehicles receive these data and possibly retransmit them to other vehicles, according to the traffic characterization protocol. All vehicles approaching the traffic jammed area receive the characterization data and have the opportunity to route around the jam.
The method of the present invention includes the steps of initializing the in-vehicle system located in a mobile unit of the present invention, listening for messages, transmitting traffic characterization data messages periodically over an ad hoc network, receiving traffic characterization data messages from the ad hoc network, processing messages received from the ad hoc network according to the traffic characterization protocol of the present invention, updating an internal traffic condition database according to messages received from the ad hoc network, and testing for change in status of the mobile unit and updating the traffic condition database accordingly.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description and its scope as pointed out in the appended claims.